Abstract: Acoustic emission (AE) events and multiple-point borehole extensometer were employed in the long term monitoring on rock mass deformation and fractures of sidewall and roof at the 4 sub-level 27 stope of Hongtoushan Copper Mine，where highly frequent ground pressure disasters occur，such as rock burst.Two observations could be derived from the deformation data comparison and different time cumulative curve of AE events:①Initial deformation is very small after a strong unloading in hard brittle rock mass，and AE events lags behind the deformation occurrence.Release of strain energy in the surrounding rock affects dissipated energy of rock mass in terms of the energy release mechanism of deformation and fracture.The dissipated energy is primary factor to result in rock mass destruction，so the deformation of surrounding rock is precondition to produce the micro fracture.②The internal structure of the rock mass has been changed due to the propagation of micro crack.In the secondary adjustment process of the stress field，fractures keep growing until generating a stable rock mass structure.Therefore，to avoid from spalling and rock burst in the hard brittle rock under high stress，an approach of increasing deformation in transient deformation of surrounding rock is suggested，which leads to improve the release strain energy of surrounding rock and hence reduce dissipated energy；Meanwhile，degradation on the internal structure of the rock mass can be prevented through setting up support system timely after excavation.Furthermore，in the field where rock burst frequently occurs，more displacement monitor equipments is suggested to lay out.Geological disasters under high stress could be forecasted by means of monitoring the sudden deformation of the surrounding rock after unloading.

Key words: Rock mechanics, High stress, Strong unloading, Acoustic emission, Multiple-point borehole extensometer